Improving Bearing Capacity of Weak Soils: A Review

Weak soils, such as soft clay and loose sand, have a poor bearing capacity, making them incapable of bearing the load of superstructures that will be imposed on them. As a result, engineers must have a solution to the issue of poor bearing capacity in weak soils before embanking into building on them.   This paper reviewed the use of stone columns, piled rafts, and geogrids for improving the bearing capability of weak soils. Important findings from recent research are also discussed. From the review of the previous researcher’s findings, it was found that modelling approaches such as physical modelling (full scale, centrifuge, laboratory scale) and numerical modelling are used to study bearing capacity improvement

Stabilisation of marine clay using polyurethane

The recent need driven by global population growth to build more infrastructures is forcing authorities to build on any soil type available within their vicinity, including weak soils like marine clay (MC). However, due to its poor engineering properties, MC is not suitable for construction purposes. Given this fact, many ground improvement techniques are being employed to improve the properties of MC and to reduce the potential damages caused by it. Although researchers have done a lot to improve the properties of MC using different materials and methods, attention has not been given to the application of polyurethane (PU) to stabilise MC. Therefore, this research focusing on the application of PU for the stabilisation of MC. The MC was characterised by testing its index and engineering properties as well as the geochemistry and microstructure. Correspondingly, PU was characterised by testing its rheological and mechanical properties alongside the microstructural analyses. The effectiveness of PU as a stabiliser was evaluated using unconfined compression tests, consolidated undrained (CU) triaxial tests and one-dimensional consolidation tests to determine the strength and stiffness. Furthermore, x-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDX) were used to discern the roots of improvement in the strength of the MC that was stabilised with PU. PU properties were also improved using reinforcing fillers. Additionally, the bearing capacity of the MC before and after treatment with PU piles was evaluated using physical and numerical models. Finally, the potential for ground contamination resulting from the application of PU to stabilise MC was investigated using toxicity characteristic leaching procedures (TCLP). The results obtained show that PU improved the shear strength and the stiffness parameters of the MC. Neutralising the acidity of MC with NaOH nearly doubled the strength and stiffness of the PU-stabilised MC. The UCS of MC that was treated with PU and NaOH improved significantly. Likewise, the secant stiffness for the CU triaxial test and tangent stiffness for the primary oedometer loading, show improvement compared to the untreated MC sample. Results of the microstructure analyses revealed that no new compounds were formed during the stabilisation of the MC with PU. The improvement in MC strength was due to the densification and coating of MC particles with PU foam. PU improved with SiO2 have superior strength, stiffness and crystallinity compared to the normal PU due to the cross-linking properties of the of SiO2 particles in the chain of PU. The results from the numerical model showed that the bearing capacity of MC that was stabilised with PU piles increases with increase in an improvement area ratio and with a length over height ratio compared to the untreated MC. The TCLP results revealed that the quantity of heavy metals present in PU is far below the regulatory limits. The results further confirmed that PU is odourless, non-corrosive and both non-cyanide and non-sulphide bearing. However, PU is capable of igniting. Overall, the potential application of PU for ground improvement is promising due to its environmental friendliness and high strength

Preliminary field survey on Mycobacterium bovis infection in cattle herds using caudal fold intradermal tuberculin test in two Northeastern States of Nigeria

Aim: A survey was conducted to determine the prevalence of bovine tuberculosis (bTB) in two states of Northeastern Nigeria, namely Bauchi and Gombe States, between February 2010 and November 2014 using caudal fold tuberculin (CFT) skin test. Materials and Methods: A total of 5489 cattle were screened using single CFT in Bauchi and Gombe States. Of the 5489 cattle, 2116 cattle were from 189 herds in five testing areas in Bauchi State and 3373 cattle in 217 herds from five testing areas from Gombe State. Results: On the basis of the CFT, herd prevalence obtained was 56.08% in Bauchi and 55.29% in Gombe State, while the individual animal prevalence was 10.96% in Bauchi and 13.73% obtained in Gombe State. The prevalence based on the testing areas in Bauchi State, Alamari had the highest prevalence with 19.4 % and Disina the lowest with 9.0 %, while in Gombe State, Wakaltu had the highest prevalence with 20.9 % and Poshereng the lowest with 8.0 %. Cows were more likely to have tuberculosis lesions than bulls (p=0.0035) in Bauchi State, but there was no significant difference in Gombe State (p=0.166). However, a statistically significant association (p<0.05) was observed among the cattle age groups with cattle ≥4 years having higher odds for tuberculin reactivity compared to those below the age of 4 years in Bauchi State only. Conclusion: There is the need to strengthen routine meat inspection and public health awareness programs on the zoonotic nature of bTB among the abattoir workers and the herdsmen

Numerical simulation with hardening soil model parameters of marine clay obtained from conventional tests

Over the last decades, numerical modelling has gained practical importance in geotechnical engineering as a valuable tool for predicting geotechnical problems. An accurate prediction of ground deformation is achieved if models that account for the pre-failure behaviour of soil are used. In this paper, laboratory results of the consolidated drain (CD) triaxial compression tests and one-dimensional consolidation tests of marine clay were used to determine the hardening soil model (HSM) parameter for use in Plaxis 3D analyses. The parameters investigated for the HSM were stiffness, strength and advanced parameters. The stiffness parameters were secant stiffness in CD triaxial compression test (E50ref), tangent stiffness for primary oedometer loading test (Eoedref), unloading/reloading stiffness (Eurref) and power for the stress-level dependency of stiffness (m). The strength parameters were effective cohesion (cref'), effective angle of internal friction (?') and angle of dilatancy (?'). The advanced parameters were Poisson’s ratio for unloading–reloading (?) and K0-value for normal consolidation (K°nc). Furthermore, Plaxis 3D was used to simulate the laboratory results to verify the effectiveness of this study. The results revealed that the stiffness parameters E50ref,Eoedref,Eurref and m are equal to 3.4 MPa, 3.6 MPa, 12 MPa and 0.7, respectively, and that the strength parameters cref', ?', ?' and K°nc are equal to 33 kPa, 17.51°, 1.6° and 0.7, respectively. A final comparison of the laboratory results with the numerical results revealed that they were in accordance, which proved the efficacy of the study

Effects of a high-dose 24-h infusion of tranexamic acid on death and thromboembolic events in patients with acute gastrointestinal bleeding (HALT-IT): an international randomised, double-blind, placebo-controlled trial

Background: Tranexamic acid reduces surgical bleeding and reduces death due to bleeding in patients with trauma. Meta-analyses of small trials show that tranexamic acid might decrease deaths from gastrointestinal bleeding. We aimed to assess the effects of tranexamic acid in patients with gastrointestinal bleeding. Methods: We did an international, multicentre, randomised, placebo-controlled trial in 164 hospitals in 15 countries. Patients were enrolled if the responsible clinician was uncertain whether to use tranexamic acid, were aged above the minimum age considered an adult in their country (either aged 16 years and older or aged 18 years and older), and had significant (defined as at risk of bleeding to death) upper or lower gastrointestinal bleeding. Patients were randomly assigned by selection of a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients received either a loading dose of 1 g tranexamic acid, which was added to 100 mL infusion bag of 0·9% sodium chloride and infused by slow intravenous injection over 10 min, followed by a maintenance dose of 3 g tranexamic acid added to 1 L of any isotonic intravenous solution and infused at 125 mg/h for 24 h, or placebo (sodium chloride 0·9%). Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was death due to bleeding within 5 days of randomisation; analysis excluded patients who received neither dose of the allocated treatment and those for whom outcome data on death were unavailable. This trial was registered with Current Controlled Trials, ISRCTN11225767, and ClinicalTrials.gov, NCT01658124. Findings: Between July 4, 2013, and June 21, 2019, we randomly allocated 12 009 patients to receive tranexamic acid (5994, 49·9%) or matching placebo (6015, 50·1%), of whom 11 952 (99·5%) received the first dose of the allocated treatment. Death due to bleeding within 5 days of randomisation occurred in 222 (4%) of 5956 patients in the tranexamic acid group and in 226 (4%) of 5981 patients in the placebo group (risk ratio [RR] 0·99, 95% CI 0·82–1·18). Arterial thromboembolic events (myocardial infarction or stroke) were similar in the tranexamic acid group and placebo group (42 [0·7%] of 5952 vs 46 [0·8%] of 5977; 0·92; 0·60 to 1·39). Venous thromboembolic events (deep vein thrombosis or pulmonary embolism) were higher in tranexamic acid group than in the placebo group (48 [0·8%] of 5952 vs 26 [0·4%] of 5977; RR 1·85; 95% CI 1·15 to 2·98). Interpretation: We found that tranexamic acid did not reduce death from gastrointestinal bleeding. On the basis of our results, tranexamic acid should not be used for the treatment of gastrointestinal bleeding outside the context of a randomised trial

Improving the strength of weak soil using polyurethane grouts: a review

The recent need to develop infrastructure, driven by global population growth is forcing societies to construct on any soil type available within their vicinity including weak soils. However, due to the poor physical and engineering properties of weak soils, they are not suitable for construction purposes. Given many ground improvement techniques that are presently employed to improve the properties of weak soils and to reduce the potential damages caused by them, this paper addresses this issue by conducting a literature review and collecting information on the application of polyurethane chemical grout for improving the properties of weak soils. While, many researchers have investigated the application of polyurethane, its application and the methods of improving the properties of weak soils, including detailed information on the application of polyurethane on weak soils for improving its properties is limited. Accordingly, this paper has examined the chemistry of each component of polyurethane and its application and explored the methods of grouting, grouting materials, the advantages and disadvantages as well as the applications of grout both in the field and in the laboratory. The review also discussed the possible means of improving polyurethane by incorporating reinforcing fillers, surfactant, catalyst and other additives. The review concluded that improved polyurethane has the potential to improve weak soil types for infrastructure development

Stabilization of Marine Clay Soil Using Polyurethane

Many chemicals stabilisation techniques are being employed all over the world to improve the engineering and physical properties of the problematic soils and reduce the potential damages caused by them. Out of those chemical stabilisation technics, application of Polyurethane to improve the strength of marine clay was investigated in the laboratory. Characterization of the soil geotechnical properties was carried out by conducting laboratory test that includes natural moisture content, Atterberg limits, grains sizes analyses, specific gravity, moisture-density relationship, unconfined compressive strength (UCS), organic matter content and PH tests. Unconfined compressive strength test at optimum moisture content with varying the dose of the Polyurethane content was conducted to test the effectiveness of Polyurethane as a chemical stabiliser. The result of the preliminary tests of the sample shows that the soil has a liquid limit of 65%, plastic limit of 26% and plasticity index of 53%. The percentages of gravel, sand and fines in the marine clay sample were 0 %, 1.32 % and 98.68 % respectively %. The results of the UCS test also revealed that Polyurethane stabilisation improved the strength of marine clay by 230%. Thus, the improvement in strength of stabilised marine clay soil can significantly reduce the overall thickness of the pavement and total cost of the road construction in future

Stabilization of Marine Clay Soil Using Polyurethane

Many chemicals stabilisation techniques are being employed all over the world to improve the engineering and physical properties of the problematic soils and reduce the potential damages caused by them. Out of those chemical stabilisation technics, application of Polyurethane to improve the strength of marine clay was investigated in the laboratory. Characterization of the soil geotechnical properties was carried out by conducting laboratory test that includes natural moisture content, Atterberg limits, grains sizes analyses, specific gravity, moisture-density relationship, unconfined compressive strength (UCS), organic matter content and PH tests. Unconfined compressive strength test at optimum moisture content with varying the dose of the Polyurethane content was conducted to test the effectiveness of Polyurethane as a chemical stabiliser. The result of the preliminary tests of the sample shows that the soil has a liquid limit of 65%, plastic limit of 26% and plasticity index of 53%. The percentages of gravel, sand and fines in the marine clay sample were 0 %, 1.32 % and 98.68 % respectively %. The results of the UCS test also revealed that Polyurethane stabilisation improved the strength of marine clay by 230%. Thus, the improvement in strength of stabilised marine clay soil can significantly reduce the overall thickness of the pavement and total cost of the road construction in future

Phytochemical screening and in-vitro antioxidant activities of aqueous and methanol extracts of Aloe vera

Background: Aloe vera L. Burman (AV) is a semi-tropical plant with many medicinal applications including wound healing, antioxidant, anti-inflammatory, and anticancer properties. It is used in Chinese medicine to treat diabetes, hypertension, infection, and dermatitis. The flowers of Aloe vera contain volatile compounds and ascorbic acid, the leaves are a good source of organic acids, phenols, enzymes, and minerals while the rind contains pectin, lignin, and polysaccharides. This study evaluated the total phenol, flavonoid, and tannin contents of aqueous and methanol extracts of Aloe vera as well as the reducing power and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities. Methods: The aqueous and methanol extracts of Aloe vera were extracted using the maceration technique. The total phenol, tannin, and total flavonoid contents of both were estimated using standard methods. The In-vitro antioxidant activities (reducing power activity and DPPH free radical scavenging activity) were also evaluated using standard methods. The EC50 and IC50 were evaluated using Non-Linear Regression. Results: Both aqueous and methanol extracts of AV revealed the presence of phenols, tannins, and flavonoids. The methanol extract produced a better-reducing power activity (EC50 = 249316 µg/ml) compared to the aqueous extract (EC50 = 463045 µg/ml) while the aqueous extract produced a better DPPH free radical scavenging activity (IC50 = 54.0 µg/ml) compared to the methanol extract (IC50 = 103.4 µg/ml). Conclusion: The reducing power and DPPH free radical scavenging activities of the two extracts are attributed to the presence of phenols, tannins, and flavonoids. It also suggests that the presence of different compounds in plants is ascribed to the solvent polarity

Effects of a high-dose 24-h infusion of tranexamic acid on death and thromboembolic events in patients with acute gastrointestinal bleeding (HALT-IT): an international randomised, double-blind, placebo-controlled trial

BackgroundTranexamic acid reduces surgical bleeding and reduces death due to bleeding in patients with trauma. Meta-analyses of small trials show that tranexamic acid might decrease deaths from gastrointestinal bleeding. We aimed to assess the effects of tranexamic acid in patients with gastrointestinal bleeding.MethodsWe did an international, multicentre, randomised, placebo-controlled trial in 164 hospitals in 15 countries. Patients were enrolled if the responsible clinician was uncertain whether to use tranexamic acid, were aged above the minimum age considered an adult in their country (either aged 16 years and older or aged 18 years and older), and had significant (defined as at risk of bleeding to death) upper or lower gastrointestinal bleeding. Patients were randomly assigned by selection of a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients received either a loading dose of 1 g tranexamic acid, which was added to 100 mL infusion bag of 0·9% sodium chloride and infused by slow intravenous injection over 10 min, followed by a maintenance dose of 3 g tranexamic acid added to 1 L of any isotonic intravenous solution and infused at 125 mg/h for 24 h, or placebo (sodium chloride 0·9%). Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was death due to bleeding within 5 days of randomisation; analysis excluded patients who received neither dose of the allocated treatment and those for whom outcome data on death were unavailable. This trial was registered with Current Controlled Trials, ISRCTN11225767, and ClinicalTrials.gov, NCT01658124.FindingsBetween July 4, 2013, and June 21, 2019, we randomly allocated 12 009 patients to receive tranexamic acid (5994, 49·9%) or matching placebo (6015, 50·1%), of whom 11 952 (99·5%) received the first dose of the allocated treatment. Death due to bleeding within 5 days of randomisation occurred in 222 (4%) of 5956 patients in the tranexamic acid group and in 226 (4%) of 5981 patients in the placebo group (risk ratio [RR] 0·99, 95% CI 0·82–1·18). Arterial thromboembolic events (myocardial infarction or stroke) were similar in the tranexamic acid group and placebo group (42 [0·7%] of 5952 vs 46 [0·8%] of 5977; 0·92; 0·60 to 1·39). Venous thromboembolic events (deep vein thrombosis or pulmonary embolism) were higher in tranexamic acid group than in the placebo group (48 [0·8%] of 5952 vs 26 [0·4%] of 5977; RR 1·85; 95% CI 1·15 to 2·98).InterpretationWe found that tranexamic acid did not reduce death from gastrointestinal bleeding. On the basis of our results, tranexamic acid should not be used for the treatment of gastrointestinal bleeding outside the context of a randomised trial.</div